Why I can't export in fbx my model?
You may want to reconsider your modeling method as it produces lots of unnecessary geometry, face intersections, and fragmented mesh with no flow.

There is no easy one-button press to clean it up quickly, but you could try the new Edit Mode Boolean operations in Blender 2.77.

By selecting one of your "shards" (a complete chunk of connected faces or geometry) and pressing Space bar and Searching for Intersect or Boolean you could let blender try and detect all intersections and cut geometry accordingly. You can then easily erase all surplus geometry by hand and repeat operation for all remaining independent chunks.